Isoalloxazines

ABSTRACT

This invention describes a series of isoalloxazines useful as antibacterial agents.

United States Patent [191 Spencer Nov. 18, 1975 [54] ISOALLOXAZINES OTHER PUBLICATIONS [75] Inventor: Claude F. Spencer, Norwich, NY.

' I l 2-1966, [73] Assignee: Morton-Norwich Products, Inc., Chemlcal Abstracts Collecnve ndex 96 12,209s, 2nd Col. Norwich, NY.

[22] Flled: Sept' 1973 Primary Examiner-Paul M. Coughlan, Jr. [21] Appl. No.: 398,753 Assistant Examiner-David E. Wheeler Attorney, Agent, or Firm-Anthony J. Franze [52] US. Cl. 260/251.5; 260/568; 260/256.4 F;

424/252 [51 lm.c1. (:07!) 475/02 ABSTRACT [58] Field of Search 260/250 Q, 251.5

This invention describes a series of lsoalloxazmes use- [56] References Cited ful as antibacterial agents.

UNITED STATES PATENTS 26 Caims, No Drawings 3,002,974 lO/l96l Petering 260/250 Q ISOALLOXAZINES This invention relates to a series of isoalloxazines of the formula: I

2 dried over MgSO and the chloroform distilled at reduced pressure to yield 111 g of red oil.

B. 7-Chloro-10pentylisoalloxazine A solution of l l 1 g (0.457 m) of 4-chloro-N-pentyl- 2-nitroani1ine (part A) in 500 ml of HOAc was shaken with hydrogen over 1V2 teaspoons of No. 28 Raney nickel catalyst, keeping the temperature below 50C. A pressure drop of 88 psi was recorded (calcd. 93 psi). After removal of the catalyst, the filtrate was stirred overnight with 73 g (0.457 m) of alloxan monohydrate and 91 g (1.47 m) of boric acid. The crude product was filtered, washed with H 0 and ether, then air-dried to yield 80 g. Recrystallization from 500 ml of dimethylformamide, with Darco, and the addition of H 0, yielded 23 g, m.p. 273275C.

Anal. calcd. for C H ClN O C, 56.52; H, 4.74; N, 17.58; Cl, 11.2. Found: C, 56.45; H, 4.72; N, 17.56; Cl, 11.04.

In accordance with the procedure of Example 1, substituting other amines in Part A, the following compounds are prepared:

Example Amine Product M.P.(C) C H N 11 n-Hexylamine 7Chloro-lO-hexylisoalloxazine 260-262 57.66 5.12 16.96 111 B-Naphthylamine 7-Chloro-lO-(B-naphthyl)isoalloxazine 378-379 63.99 2.93 14.96 1V Benzylamine 7-Chlorol O-benzylisoalloxazine 336-340 59.89 3.30 16.75 V Phenethylamine 7-Chloro-lO-phenethylisoalloxazine 307-308 60.89 3.70 15.91 V1 p-Toluidine 7Ch1oro l O-(p-tolyl)isoalloxazine 339-341 60.30 3.25 16.60 V11 p-Ethylaniline 7-Chloro- 1 0-(p-ethylphenyl)isoalloxazine 293-295 61.33 3.70 15.82 V111 pAnisidine 7-Ch1oro-10-(p-anisyl)isoalloxazine 334-335 57.40 3.09 15.90 [X p-Phenetidine 7-Chloro-10-(p-ethoxyphenyl)isoalloxazine 294-298 58.1 1 3.66 15.12 X p-Butoxyaniline 7-Chloro-l0-(p-butoxyphenyl)isoalloxazine 255-260 60.13 4.31 14.26 X1 3 ,4Dichloroaniline 7-Chlorol 0-(3,4-dichlorophenyl)isoalloxazine 344-346 48.69 1.78 14.16

The members of the series of isoalloxazines herein described are effective antibacterial agents. They are adapted to be combined with various excipients and adjuvants known in the art to provide conveniently employed forms such as dusts, solutions, suspensions, sprays, unguents and the like capable of controlling and eradicating susceptible bacterial growth. They are particularly inimical to organisms such as Staphylococcus aureus, Corynebacterium liquefaciensand Hemophilus vaginalis concentrations of them ranging from one part per twenty thousand to one part per million of media being capable of inhibiting the growth ofsuch organisms under the commonly employed serial dilution technique for ascertaining antibacterial potency.

The methods currently favored for preparing the members of this series of isoalloxazines are set forth in the following examples:

EXAMPLE 1 7-Chlorol O-pentylisoalloxazine A. 4-Chloro-N-pentyl-2-nitroaniline A mixture of 110 g (0.57 m) of 1,4-dichloro-2-nitrobenzene, 100 g (131 ml, 1.15 m) of n-pentylamine, m1 of H 0 and 300 ml of dimethylformamide was heated at reflux overnight. The reaction solution was then poured into 4 liters of ice water. The water was decanted and the red oil dissolved in 300 ml of ethanol, Darco added, and the mixture filtered. The filtrate was then poured into 4 liters of ice water. The mixture was extracted with chloroform, the chloroform solution EXAMPLE X11 7,8-Dichloro- 1 O-propylisoalloxazine A. 4,5-Dichloro-N-propyl-2-nitroaniline A solution of 22.6 g (0.1 m) of 2,4,5-trichloronitrobenzene, 42 ml (30 g, 0.5 m) of n-propylamine and 200 m1 of ethanol was heated at reflux overnight. The reaction mixture was then chilled and filtered and the product washed and air-dried to give 18 g, m.p. 53-57C.

B. 7,8-Dichloro-10-propylisoalloxazine A solution of 18 g (0.07 m) of 4,5-dichloro-N-propyl- 2-nitroaniline (part A) in m1 of HOAc was shaken with hydrogen over one-half teaspoon of No. 28 Raney nickel catalyst, keeping the temperature below 50C. After a pressure drop of 15 psi (calcd, 14.5 psi) the catalyst was removed by filtration. The filtrate was then stirred overnight at room temperature with 11.5 (0.07 m) of alloxan monohydrate and 13.4 g (0.21 m) of boric acid. The mixture was filtered and the solid washed with H O, ethanol and ether, then air-dried to give 21.5 g. Recrystallization from 50 ml of dimethylformamide with Darco, followed by a second recrystallization from 300 ml of HOAc and H 0, resulted in 12 g of product, m.p. 310-31 1C.

Anal. calcd, for C H Cl N O C, 48.02; H, 3.10; N, 17.23; Cl, 21.81. Found: C, 47.75; H, 3.16; N, 17.07; Cl, 21.77.

In accordance with the procedure of Example X11, substituting other amines in Part A, the following compounds are prepared:

Example Amine Product M.P.(C) C H N C1 X111 lsopropylamine 7.8-Dichloro-lO-isopropylisoalloxazine 38 l382 47.68 3.12 17.43 21.79 XlV Aniline 7,8-Dichloro-lO-phenylisoalloxazine 372-376 53.32 2.21 15.55 19.91

EXAMPLE XV 7-Chloro-3-methy1-lO-phenylisoalloxazine A. 4-Chloro-N-phenyl-2-nitroaniline A solution of 192 g (1.0 m) of 1,4-dich1oro-2nitrobenzene, 82 g (1.0 m) of sodium acetate and 300 ml (475 g, 5.1 m) of aniline was heated overnight at reflux, allowed to cool, then poured into 4 liters of ice water. The oil layer containing the product was separated from the aqueous layer and crystallized from 2000 ml of ethanol with Darco, and H added to the cloud point. After standing 4 days, 1 13 g, m.p. 586lC., was obtained.

B. 7-Chlorol O-phenylisoalloxazine A solution of 59.5 g (0.24 m) of 4-chloro-N-phenyl- Z-nitroaniline (Part A) in 500 ml of HOAc was shaken with hydrogen over 2 teaspoons of No. 28 Raney nickel catalyst. A pressure drop of 48 psi (calcd. 48.2 psi) was observed. The catalyst was filtered, and the filtrate stirred overnight at room temperature with 38.4 g (0.24 m) of alloxan monohydrate and 44.5 g (0.72 m) of boric acid. The crude product was removed by filtration, washed with H O, ethanol, and ether to give 82 g, unmelted at 405C. Recrystallization from 2000 ml of dimethylformamide, with Darco, and H 0 added to the cloud point yielded 33 g, m.p. 384386C.

Anal. calcd. for C l-l ClN O C, 59.18; H, 2.79; N, 17.26; Cl, 10.92. Found: C, 59.10; H, 2.97; N, 17.35; C1, 10.73.

C. 7-Chloro-3-methyll O-phenylisoalloxazine To a suspension of 40 g (0.12 m) of B in 1 liter of dimethylformamide was added g (0.12 m) of sodium hydride (60% in mineral oil) with stirring and heating on the steam bath. A dark solution was soon effected. After further heating with stirring for 1 /2 hr, 19 g (20% excess) of dimethyl sulfate was added in about 5 min. During this period, the reaction mixture gradually turned to orange-red while solid started to separate.

After 2 hr of heating and stirring, the mixture was allowed to cool and then filtered. The orange solid was washed with dimethylformamide and air-dried. It was further triturated well with water, filtered, washed with water and dried. The yield was 22 g (53%).

Recrystallization of 2 g from 100 ml of dimethylformamide gave 1.3 g of analytically pure product, m.p. 400.

Anal. calcd. for C H ClN O C, 60.27; H, 3.27; N, 16.54. Found: C, 60.19; H, 3.28; N, 16.58.

EXAMPLE XVI 7-Chloro-3 2-hydroxyethyl l O-phenylisoalloxazine To a suspension of 49 g (0.15 m) of the compound of Example XV, B, in 1 liter of dimethylformamide was added 6 g (0.15 m) of sodium hydride (60% in mineral oil) with stirring on the steam bath. A clear solution was obtained after 1 /2 hr of heating and stirring and then 20 g (0.25 m) of ethylene chlorohydrin was added. The mixture was further heated for 3% hr and then allowed to stand overnight.

The mixture was poured onto cracked ice and allowed to stand for a few hours. The solid was collected, washed well with water and dried at The yield was 37.5 g (88%).

Recrystallizationof 5.4 g from 35 ml of dimethylformamide and water gave 3.5 g of analytically pure product, m.p. 283285.

Anal. calcd. for C H ClN O C, 58.26; H, 3.55; N, 15.20. Found: C, 58.42; H, 3.63; N, 15.35.

EXAMPLE XVII 3-Benzyl-7-chlorolO-phenylisoalloxazine To a mixture of 49 g (0.15 m) of the compound of Example XV, B, in 1.2 liters of dimethylformamide was added 7 g (0.18 m) of sodium hydride (60% in mineral oil) on the steam bath with stirring. After a clear solution was obtained, 30 g (0.18 m) of benzyl bromide was added through the condenser. After 2 hr of heating and stirring, the reaction mixture was poured onto cracked ice and allowed to stand for a few hours.

The solid was collected, washed well with water and dried at 100. The yield was 44 g (71%).

Recrystallization of 1 g from ethanol ml) and acetonitrile (5 ml) gave 0.7 g of analytically pure product, m.p. 293296.

Anal, calcd. for C H ClN O C, 66.59; H, 3.64; N, 13.51. Found: C, 66.45; H, 3.65; N, 13.47.

EXAMPLE XVIII 10-Isopropyl-7-nitroisoalloxazine A. N-lsopropyl-4-nitro-o-phenylenediamine A slow stream of H 5 was passed into a mixture of 338 g (1.5 m) of N-isopropyl-2,4-dinitroaniline, 1200 ml of 28% NH OH and 2400 ml of ethanol, keeping the temperature at 4555C. During the 2 hr addition, the yellow mixture became a dark purple solution. Stirring was continued at 455 5C for 60 minutes after the addition. The reaction mixture was chilled, and the redorange crystals which precipitated were filtered off, washed with H 0, and air-dried to give 225 g, m.p. 7l75C.

The H 5 reduction of the 225 g (mixture of the dinitroaniline and diamine) was repeated, using 925 ml of 28% NH OH and 1850 m1 of ethanol. After air-drying the yield was 84 g, m.p. 113l15C.

lO-lsop ropyl-7-nitroisoalloxazine A mixture of 84 g (0.043 m) of N -isopropyl-4-nitroo-phenylenediamine (part A), 69 g (0.043 ml)-of alloxan monohydrate, 79.8 g (1.29 m) of boric acid and 500 ml of HOAc was stirred overnight. The orange solid was filtered washed with H O, ethanol, and ether and air-dried to give 141 g. Recrystallization from 600 ml of dimethylformamide, withDarco, and the addition of 60 ml of H 0 to the filtrate, yielded 85 g, m.p. 363-367.

Anal. calcd. for C H N O C, 51.83; H, 3.68; N, 23.25. Found: C, 51.63; H, 3.60; N, 23.57.

EXAMPLE XIX 10-Butyl-7-nitroisoa1loxazine A. N -Butyl-4-nitro-o-phenylenediamine A slow stream of H 8 was passed into a mixture of 310 g (1.3 m) of N-butyl-2,4-dinitroaniline, 1200 ml of 28% NH OH and 2400 ml of ethanol, keeping the temperature at 4555C. Stirring was continued at 4555C for 60 minutes after the H S addition, then the reaction mixture was cooled overnight, filtered, washed with H 0, and air-dried to give 218 g. Recrystallization from 500 ml of toluene yielded 180 g, m.p. 106108C.

B. lO-Butyl-7-nitroisoalloxazine A mixture of 125 g (0.6 m) of N-butyl-4-nitro-ophenylenediamine (part A), 96 g (0.6 m) of alloxan monohydrate, 1 l 1 g 1.8 m) of boric acid and 1000 ml of HOAc was stirred overnight. The yellow precipitate was filtered off, washed with H O, SDA-32 and ether, then air-dried. The 121 g of crude product was recrystallized from 300 ml of dimethylformamide, with Darco, followed by a second recrystallization from 300 ml of dimethylformamide and 150 ml of H and ovendried (110C) to yield 43 g, m.p. 255258C.

Anal. calcd. for C H, N O C, 53.33; H, 4.16; N, 22.22. Found: C, 53.57; H, 4.35; N, 22.36.

EXAMPLE XX lO-Methoxyethyl-7-nitroisoalloxazine A. N-Methoxyethyl-2,4-dinitroaniline To a warmed solution of 101.5 g (0.5 m) of l-chloro- 2,4-dinitrobenzene and 300 ml of dimethylformamide was added slowly, 115.5 g (1.0 m) of 65%70% 2- methoxyethylamine in water. The solution was heated under reflux for 5 hr, during which time an orange crystalline solid separated. The mixture was chilled, the product filtered, washed and air-dried to yield 117 g, m.p. l42-148C.

B. N-Methoxy-4-nitro-o-pheny1enediamine A slow stream of H S was passed into a solution of 117 g (0.49 m) of N-methoxyethyl-Z,4-dinitroaniline (part A), 448 ml of 28% NH OH and 896 ml of ethanol, maintaining a tempera ure of.4555C. Stirring was continued at 45-55C or 60 min. following the 4 hr addition. After chilling overnight, the mixture was filtered, washed with H 0 and air-dried to give 63 g, m.p. 101104C.

C. 10-Methoxyethyl-7-nitroisoalloxazine A mixture of 63 g (0.30 m) of N-methoxyethyl-4- nitro-o-phenylenediamine (part B), 47.7 g (0.30 m) of alloxan monohydrate, 54.8 g (0.89 m) of boric acid and 400 ml of HOAc was stirred overnight at room temperature. The precipitated product was collected by filtration, washed with H O, ethanol, and ether, then airdried to give 129 g. Recrystallization from 800 ml of dimethylformamide, with Darco, and H 0 added to the cloud point yielded 64 g, m.p. 307308C.

Anal. calcd. for C H N O C, 49.21; H, 3.49; N, 22.08. Found: C, 4924; H, 3.49; N, 22.27.

EXAMPLE XXI l0-Ethoxyethyl-7-nitroisoa1loxazine A. N-Ethoxyethyl-2,4-dinitroaniline A solution containing 101.5 g (0.5 m) of l-chloro- 2,4-dinitrobenzene, 89.1 g (1.0 m) of ethoxyethylamine and 300 ml of dimethylformamide was heated at reflux for 5 hrs then chilled overnight. The yellow precipitate was filtered, and H 0 added to the filtrate. The product was filtered, washed with H 0, and air-dried to give 112 g, m.p. 7478C.

B. N-Ethoxyethyl-4-nitro-o-phenylenediamine A slow stream of H 5 was passed into a mixture of 1 12 g (0.44 m) of N-ethoxyethyl-2,4-dinitroaniline (part A), 405 ml of 28% NH OH and 810 ml of ethanol. A temperature of 45-55C was maintained throughout the 4 hr addition and for 60 min. following the addition. The mixture was chilled overnight, then filtered and washed with 11 0 and air-dried to yield 52 g, m.p. 8688C.

C. 10-Ethoxyethyl-7-nitroisoalloxazine A mixture of 52 g (0.23 m) of N -ethoxyethyl-4- nitro-o-phenylenediamine (part B), 36.9 g (0.23 m) of alloxan monohydrate, 42.9 g (0.69 m) of boric acid and 375 ml of HOAc was stirred overnight at room temperature. The crude product was filtered, washed with H O, ethanol, and ether, then air-dried to give 93 g. Recrystallization from 300 ml of dimethylformamide, with Darco, and H 0 added to the cloud point, gave 21 g, m.p. 265267C.

Anal. calcd. for C H N O C, 50.75; H, 3.96; N, 21.14. Found: C, 50.87; H, 3.89; N, 21.13.

EXAMPLE XXII l0-Ethyl-7-trifluoromethylisoalloxazine A. N-Ethyl-4-trifluoromethyl-2-nitroaniline To a heated solution of 113 g (0.5 mole) of 2-nitro-4- trifluoromethyl chlorobenzene in 200 ml of ethanol was added slowly 200 ml (2.2 mole) of ethylamine. The solution was heated at reflux for 30 minutes after the addition then allowed to cool overnight. The product was filtered, washed with ethanol-ether, and air-dried to yield 111 g, m.p. 5455C.

B. 10-Ethyl-7-trifluoromethylisoalloxazine A mixture of 104 g (0.44 mole) of N-ethyl-4-trifluoromethyl-2-nitroaniline (part A) in 800 ml of HOAc was shaken with hydrogen over two teasspoonsful of No. 28 Raney nickel catalyst. The pressure drop was 98.5 psi. (calcd. psi). After removal of the catalyst by filtration, the filtrate was stirred overnight with 71 g (0.44 mole) of alloxan monohydrate and 82 g (133 mole) of boric acid. The crude product was filtered, washed with H O, ethanol and ether and recrystallized from 1250 ml of dimethylformamide, with Darco, and ml of H 0 added to the filtrate. The yield was 40 g, m.p. 330332C.

Anal. calcd. for C, H F N O C, 50.33; H, 2.92; N, 18.06. Found: c, 50.32; H, 2.92; N, 18.14.

In accordance with the procedure of Example XXII, substituting other amines in Part A, the following compounds are prepared:

Example Amine Product M.P.( c") c H N XXIII Isopropylamine 7-Trifluoromethyl-lo -isopropylisoalloxazine 292-293 51.62 3.32 17.41 xxrv Aniline 7-Trifluoromethyl-lO-phenylisoalloxazine 338-341 56.86 2.51 15.84

EXAMPLE XXV 10-( p-Anisyl )-7-chloro-8-met11ylisoalloxazine A. N-(p-Anisyl)-4-chloro-5-methyl-2-nitroaniline A mixture of 83 g (0.29 m) of 2-ch1oro-4,5-dinitrotoluene, 71.3 g (0.58 m) of p-anisidine and 500 ml of ethanol was heated at reflux for 36 hours. It was then poured into 4 liters of ice water. The water was decanted from the black oil which had separated and dissolved in 500 ml of CHC1 dried over anhydrous MgSO and the CHCL distilled at reduced pressure to yield a dark oil, weighing 65 g.

B. lO-(p-Anisyl)-7-chloro-S-methylisoalloxazine A mixture of 65 g (0.22 m) of N-anisyl-4-chloro-5- methyl-2-nitroaniline (part A), 1 teaspoon of No. 28 Raney nickel catalyst and 300 ml of HOAc was shaken with hydrogen. After a pressure drop of 47 psi (calcd. 43.8 psi), the catalyst was removed by filtration. To the filtrate was added 35 g (0.22 m) of alloxan monohydrate and 40 g (0.65 m) of boric acid. After stirring overnight, the crude product was filtered, washed with H O, ethanol and ether, then air-dried to give 75 g. Recrystallization from 1000 ml of dimethylformamide, with Darco, and H yielded 36 g, m.p. decomposes 3133l5C.

Anal. calcd. for C ,,h ClN O C, 58.62; H, 3.55; N, 15.20; Cl, 9.61. Found: C, 58.50; H, 3.52; N, 15.32; C], 9.62.

EXAMPLE XXVI 7-Bromo- IO-ethylisoalloxazine A. 4-Bromo-N-ethyl2-nitroaniline A mixture of 200 g (0.72 mole) of 2,5-dibromonitrobenzene, 330 ml (161 g, 3.58 mole) of 70% ethylamine and 300 ml of dimethylformamide was heated under reflux overnight. The reaction mixture was chilled in an ice bath, and the product removed by filtration and airdried to give 129 g, m.p. 7783C.

B. 7-Bromo-lO-ethylisoalloxazine A solution of 87 g (0.38 mole) of 4-bromo-10-ethyl- 2-nitroaniline (part A) in 500 ml of l-IOAc was shaken with hydrogen over 1 teaspoonful No. 28 Raney nickel catalyst, keeping the temperature below 50C. A pressure drop of 71 psi was recorded (calcd. 75.5 psi). The catalyst was removed by filtration. A second run was made in the same manner. The combined filtrates were stirred overnight at room temperature with 120 g (0.75 mole) of alloxan monohydrate and 130 g (2.25 mole) of boric acid. The crude product was filtered, washed with H O, ethanol, and ether, then air-dried to give 250 g. Recrystallization from 3200 ml, of dimethylformamide, with Darco, and H 0 added to the cloud point yielded 38 g, m.p. 320321C dec.

Anal. calcd. for C H BrN O C, 44.88; H, 2.82; N,

17.45; Br, 24.88. Found: c, 44.97; H, 2.76; N, 17.37;

The antibacterial potency of members of this series of isoalloxazines as determined by the commonly used serial dilution technique is set forth below:

Table Continued Compound MinimaI Inhibitory of Example Concentration in meg/ml 1X 50 6.25 6.25 X 6.25 3.1 12.5 X1 0.75 25 X11 12.5 6.25 625 X111 12.5 12.5 12.5 XIV 25 3.1 6.25 )XV; 50 50 25 25 6.25 XVII 6.25 6.25 XVlll 25 12.5 XIX 50 25 50 XX 25 50 XXI I00 25 6.25 XXII 25 12.5 25 XXIII 50 50 25 XXIV 50 3.1 25 XXV 50 6.25 25 XXVI 50 12.5 25

In the above. A represents .S'Iaplzylnuxmx aureux; B represents (.nn-m'lmrreriun| lu lmjunenx: and C represents Henmphilus vagina/is.

l 5. The compound 3-methyl-7-chloro- 10- phenylisoalloxazine.

16. The compound 3 -(2-hydroxyethyl)-7-chloro-10- phenylisoalloxazine.

17. The comp ound 3-benzyl-7-chloro-10- phenylisoalloxazine.

18. The compound 7-nitro-lO-isopropylisoalloxazine.

19. The compound 7-nitro-10-buty1isoalloxazine.

20. The compound 7-nitro-l0-methoxyethylisoalloxazme.

21. The compound 7-nitro-IO-ethoxyethylisoalloxazine.

22. The compound 7-trifluoromethyl-l0-ethylisoalloxazine.

The compound propylisoalloxazine.

24. The compound 7-trifluoromethyl-10-phenyl1soalloxazine.

7-trifluoromethyll 0-iso- 25. The compound 7-chloro-8-methyl-IO-(p-anisyl- )isoalloxazine.

26. The compound 7-bromo-l0-ethylisoalloxazine. l 

1. THE COMPOUND 7-CHLORO-10-PETYLISOALLOXAZINE.
 2. The compound 7-chloro-10-hexylisoalloxazine.
 3. The compound 7-chloro-10-( Beta -naphthyl)isoalloxazine.
 4. The compound 7-chloro-10benzylisoalloxazine
 5. The compound 7-chloro-10-phenethylisoalloxazine.
 6. The compound 7-chloro-10-(p-tolyl)isoalloxazine.
 7. The compound 7-chloro-10-(p-ethylphenyl)isoalloxazine.
 8. The compound 7-chloro-10-(p-anisyl)isoalloxazine.
 9. The compound 7-chloro-10-(p-ethoxyphenyl)isoalloxazine.
 10. The compound 7-chloro-10-(p-butoxyphenyl)isoalloxazine.
 11. The compound 7-chloro-10-(3,4-dichlorophenyl)isoalloxazine.
 12. The compound 7,8-dichloro-10-propylisoalloxazine.
 13. The compound 7,8-dichloro-10-isopropylisoalloxazine.
 14. The compound 7,8-dichloro-10-phenylisoalloxazine.
 15. The compound 3-methyl-7-chloro-10-phenylisoalloxazine.
 16. The compound 3-(2-hydroxyethyl)-7-chloro-10-phenylisoalloxazine.
 17. The compound 3-benzyl-7-chloro-10-phenylisoalloxazine.
 18. The compound 7-nitro-10-isopropylisoalloxazine.
 19. The compound 7-nitro-10-butylisoalloxazine.
 20. The compound 7-nitro-10-methoxyethylisoalloxazine.
 21. The compound 7-nitro-10-ethoxyethylisoalloxazine.
 22. The compound 7-trifluoromethyl-10-ethylisoalloxazine.
 23. The compound 7-trifluoromethyl-10-isopropylisoalloxazine.
 24. The compound 7-trifluoromethyl-10-phenylisoalloxazine.
 25. The compound 7-chloro-8-methyl-10-(p-anisyl)isoalloxazine.
 26. The compound 7-bromo-10-ethylisoalloxazine. 